Hmm...
-Mew, as evidenced in
Mewtwo Strikes Back, would clearly be able to handle Mewtwo.
-Lugia, Ho-oh, Groudon, Kyogre, Rayquaza, Lucario, and all the other legendary trios and Mew-esque Pokemon (barring Jirachi, Uxle and Victini) would likely get flung by pwning Psychic attacks
-Jirachi could just use Doom Desire and wish for Mewtwo's demise; Uxle could just open its eyes and cause Mewtwo to go "HERPDERP WHUT IZ A PSYCHIC ATTACK", and if Victini sneaks in V-Generate first, Mewtwo is a GONER.
-Deoxys handled Rayquaza pretty good and can regenerate itself, not to mention its superior Forme-switching ability. I'd say it has a pretty good shot at tying with Mewtwo or even surpassing it. Attacks in Attack Forme would be greatly advantageous, especially if Deoxys uses its naturally-higher speed to dispatch Mewtwo with a powerful technique.
-Regigigas would likely get pummeled before it could even land a hit
-Dialga could reverse time to shift Mewtwo to its embryotic in-vitro stage and squish Mewtwo (whose Psychic powers would be underdeveloped at that point and are resisted by Steel-typing anyway) as it writhes helplessly.
-Palkia could pull a few spacial tricks, but Mewtwo would probably end up overpowering it at some point...
-Giratina could just use Shadow Force to fade away and strike/ninja Mewtwo with a super-effective ramming. Giratina could also just yank Mewtwo into the Distortion World and gain the upper hand in battle due to home field/turf advantage.
-Heatran would resist Psychic, but Focus Blast could probably dispose of it in a matter of minutes.
-The Lati@s duo is pretty potent with Soul Dew, not to mention their ferocious Dragon-type capabilities and Psychic-type abilities.
-Cresselia...not really seeing it put up much of a fight.
-Arceus would just switch Plates and relentlessly
slam Mewtwo with a STAB Dark-type Judgment due to Dread Plate.
-Reshiram, Zekrom, and Kyuremu would
start out by holding their own, but getting mentally broken in the end, primarily due to their shoddy movepools.
-I heard Genosect had some nuke/warhead on its back, so it's a contender
by default. And it can change cassettes!
-Zoroark also gets special mention; its illusory abilities might be able to confuse and confound Mewtwo, where it can follow up with a damaging Dark-type attack!
Roughly, in order of contending ability against Mewtwo...
Mew/Arceus, Dialga, Jirachi/Victini/Uxle, Genosect/Deoxys, Giratina, Lati@s, Palkia/Zoroark, Reshiram/Zekrom/Kyuremu...and pretty much everyone else.
-3- I think Arceus is WAY too over-rated... Who cares if he's the friggin' creator of pokemon? A Lucario could beat one with no plate hands down.
As for the question, I'd have to go with a Reshiram or Zekrom. They're DRAGONS for pete's sake... -3-
Arceus inherently
is should be(?) aware of every Pokemon's weakness...if anything, Mewtwo is overrated. Just get something with Psychic to use Imprison and no more BA Mewtwo. :cer_laugh: And Arceus would probably outspeed Lucario and lay waste with an Overheat or Earthquake,
sans Plate(s), before Lucario even lays a paw on him.
And as G.K. Chesterton wisely explained:
[FONT=verdana,arial,helvetica][FONT=verdana,arial,helvetica]Fairy tales do not tell children the dragons exist. Children already know that dragons exist. Fairy tales tell children the dragons can be [/FONT][/FONT]killedKO'd.
;)